In conventional testing systems, there is an adapter between the test specimen and the full-grid cassette with the test probes. This adapter has apertures at the places where the test specimen has contact points. The probes are guided through these apertures in the adapter and thus they are able, even in an inclined position, to contact the test specimen at the connection points. However, these conventional testing systems are not capable of testing printed circuit boards with high conductive-trace densities.
In DE-Z "Galvanotechnik" 87, (1996), No. 7, pp. 2358 to 2360, there is an illustration of an arrangement which enables very fine structures to be electrically tested. Under the test specimen, there is a probe adapter which has apertures at the contact points of the test specimen. Between the probe adapter and the full-grid cassette with the test probes, there is a simple printed circuit board acting as a translator. This translator has the same contact pattern on the adapter side as the test specimen. The contact pattern on the other side of the translator is that of the full-grid cassette. The contact points of the test specimen and the translator are connected through the adapter apertures by means of probes. The contact points of the upper and lower side of the translator are interconnected via conductive traces and feed-throughs. With this arrangement it is possible to perform a parallel electrical test of all contact points on the test specimen.
For the next generation of printed circuit boards, however, this variant, too, comes up against its limits. Even thinner probes in the adapter lead to very high costs or can no longer be manufactured. In addition the reliability of the contacts decreases.
Another arrangement, which can test even printed circuit boards with high conductive-trace densities, is the serial finger test system. In this system the contact points are tested one after the other for short circuit and open circuit faults. Substantially more time is required for this. Given the ever increasing number of contact points it is only possible to test the next generation of printed circuit boards using finger test systems by expending a considerable amount of time.
DE-OS 42 37 591 discloses an adapter foil having test areas with very fine structures. However, reliable contact with the test specimen is not guaranteed as each printed circuit board is slightly uneven, and the contact areas on the printed circuit board may even be displaced. For this reason too great a pressure is exerted on some connection areas, which can destroy the contact areas on the printed circuit board and the adapter foil, while on other contact areas the surface pressure is too slight, so that the contact resistance is too high, resulting in incorrect electrical measurements.